Add TranslationKeys type (#154)

.changeset/olive-crews-repeat.md

@@ -0,0 +1,31 @@
+---
+'@vocab/core': minor
+---
+
+Add `TranslationKeys` type
+
+The `TranslationKeys` type can be used to get a string literal union of all the translation keys used in a translation file.
+
+**EXAMPLE USAGE**
+
+```jsonc
+// .vocab/en.translations.json
+{
+  "Hello": {
+    "message": "Hello"
+  },
+  "Goodbye": {
+    "message": "Goodbye"
+  }
+}
+```
+
+After running `vocab compile`:
+
+```tsx
+import type { TranslationKeys } from '@vocab/core';
+import translations from './.vocab';
+
+// 'Hello' | 'Goodbye'
+type Keys = TranslationKeys<typeof translations>;
+```

packages/core/src/types.ts

@@ -75,6 +75,10 @@ export type TranslationFile<
   load: (language: Language) => Promise<void>;
 };
 
+export type TranslationKeys<
+  Translations extends TranslationFile<any, ParsedFormatFnByKey>,
+> = keyof Awaited<ReturnType<Translations['getMessages']>>;
+
 export interface LanguageTarget {
   // The name or tag of a language
   name: LanguageName;